Encapsulated energy-dissipative fuse for integrated circuits and method of making the same

ABSTRACT

A laser-programmable fuse structure for an integrated circuit device is disclosed. In an exemplary embodiment of the invention, the fuse structure includes a conductive layer, the conductive layer completing a conductive path between wiring segments in a wiring layer. An organic material is encapsulated underneath the conductive layer, wherein the fuse structure is blown open by application of a beam of laser energy thereto.

BACKGROUND

[0001] The present invention relates generally to integrated circuitdevices and, more particularly, to an encapsulated, energy-dissipativefuse for use with integrated circuit devices such as a dynamic randomaccess memory (DRAM).

[0002] Semiconductor integrated circuits (ICs) and their manufacturingtechniques are well known. In a typical integrated circuit, a largenumber of semiconductor devices are fabricated on a silicon substrate.To achieve the desired functionality of the IC, a plurality ofconductors (i.e., metallization layers) are provided to electricallyconnect selected devices together. In some integrated circuits,conductive lines are coupled to fuses, which fuses may be cut or blownto create an open circuit. For example, in a dynamic random accessmemory (DRAM) circuit, fuses may be used in conjunction with isolatingfailing memory array elements and replacing them with redundant arrayelements. In logic circuits, fuses may also be used to select or modifycertain circuit performance or functions.

[0003] Laser fusible links are one example of such fuse devices, and aregenerally formed from conductive lines that can be explosively fusedopen by the application of laser energy thereto. The applied laserenergy causes a portion of the link material to vaporize and a portionof the material to melt. Typically, the fusible link is relativelynarrow as compared to the remainder of the conductive structure, and maybe composed of materials such as aluminum or polysilicon. Alternatively,a fuseable link may be made of the same metal material as the chipconductors themselves.

[0004] In order to intentionally blow such a fuse, a short pulse oflaser energy is impinged upon the fuse at a predetermined spot thereon.Since every fuse in an IC is not necessarily blown by design, care istaken to ensure that adjacent fuses are not blown by the applied laserenergy. Because of the possibility of laser-induced damage, the areasunderlying the fuses are typically devoid of semiconductor devices(e.g., transistors) and the fuses are spaced relatively far apart inconventional systems. Another existing approach to preventing theunintentional blowing of adjacent fuses is to reduce the intensity ofthe applied laser energy. However, in so doing, it is possible that thefuse material might not completely be ablated or vaporized by the laser.As a result, any fuse material removed by the laser could simply beliquified and then re-solidified, thereby potentially causing a shortcircuit of an adjacent fuse or device, perhaps even reclosing the veryfuse sought to be blown open.

[0005] On the other hand, the absorption of excessive laser energy by anIC device may also result in unwanted damage to the IC substrate or toan insulating layer(s) adjacent to the fuse device. With the use of socalled “low-κ” (low dielectric constant) materials as insulating layersbecoming increasingly common in IC fabrication, there is an increasedemphasis on reducing the amount of laser energy needed to blow a fuse,since these low-κ materials are generally more susceptible tolaser-induced damage. Accordingly, it becomes a difficult proposition todesign a fuse structure which is capable of blowing with lower appliedlaser energy, but still sufficiently ablates so as not to result inshort circuiting of other components.

BRIEF SUMMARY

[0006] The above discussed and other drawbacks and deficiencies of theprior art are overcome or alleviated by a laser-programmable fusestructure for an integrated circuit device. In an exemplary embodimentof the invention, the fuse structure includes a conductive layer, theconductive layer completing a conductive path between wiring segments ina wiring layer. An organic material is encapsulated underneath theconductive layer, wherein the fuse structure is blown open byapplication of a beam of laser energy thereto.

[0007] In a preferred embodiment, a liner material is in electricalcontact with the wiring segments and the conductive layer, the linermaterial further encapsulating the organic material between the wiringlayer and the conductive layer. The organic material is selected from agroup that includes a polyimide, a polyamide, a polyarlyene ether, apolyaromatic hydrocarbon (PAH), and a conductive polyaniline. The linermaterial and conductive layer are selected from a group that includesTaN, Ta, TiN, Ti, W, WN, TaSiN, TiSiN, or alloys therefrom.

[0008] Preferably, the fuse structure further includes a pair of viasformed within an insulating layer and extending down to the wiringsegments. A mesa region of the insulating layer is thereby formedbetween the pair of vias, wherein the liner material is formed uponsides of the mesa region and the wiring segments. The pair of vias isfilled with the organic material, which further occupies an inner areaof the fuse structure. The inner area is between the top of the mesaregion and the conductive layer. The conductive layer covers the innerarea and the organic material, thereby completing the conductive path.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Referring to the exemplary drawings wherein like elements arenumbered alike in the several Figures:

[0010]FIGS. 1 through 8 are cross-sectional views of a method forforming an encapsulated, energy-dissipating fuse structure, inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0011] A novel fuse structure and accompanying method for forming thesame is disclosed herein which overcomes or alleviates the abovedescribed drawbacks. Broadly stated, an organic material is encapsulatedbeneath a thin, conductive layer, thereby forming a fuse structure thatcan be blown by a relatively low-energy laser beam. When the conductivelayer is subjected to laser energy, the encapsulated organic materialtherein is rapidly volatized, thus explosively opening the fuse.

[0012] Referring generally to FIGS. 1 through 8, there is illustrated amethod for forming an encapsulated, energy-dissipating fuse structure,in accordance with an embodiment of the invention. In FIG. 1, asemiconductor wafer 10 has a passivation or insulating layer 12 formedthereupon as topmost level of a semiconductor device. Passivation layersare well known in the art and provide a measure of protection for thelower level components (e.g., metallization layers) from oxidation andexternal moisture penetration, among other things. In addition,passivation layer 12 may serve as a diffusion barrier against the upwarddiffusion of metallic atoms (e.g., copper) from the lower levels of thesemiconductor device. Examples of passivation layer 12 include, but arenot limited to, silicon dioxide (SiO₂), silicon nitrides (SiN_(x)),silicon oxynitrides (SiO_(x)N_(y)), silicon carbides (SiC), etc., orcombinations thereof. In the embodiment shown, a upper metallizationlayer 14 includes wiring segments 16 to be joined by a fuse structure.Wiring segments 16 may be made from a conductive material such ascopper, aluminum, tungsten, silicon, etc., or combinations thereof.

[0013] Next, a pair of vias (openings) 18 are formed through passivationlayer 12 by standard lithography, etching and cleaning techniques, suchthat vias 18 extend down to (and are at least partially aligned with)the ends of wiring segments 16. Although a dry plasma etching process ispreferred, any suitable etching techniques may be implemented. Thedistance between the outer ends of vias 18 will ultimately determine thelength of the fuse structure. As a result of the etching of vias 18, amesa 20 of passivation material is defined therebetween. In FIG. 2, aportion of the mesa 20 is subsequently removed by additionalphotolithography, etching and cleaning steps, thereby defining an innerarea 22 of the fuse structure.

[0014] Referring now to FIG. 3, a liner material 24 is formed over thetop of passivation layer 12, as well as the sides and bottom of vias 18and the top of mesa 20. Liner material 24 is a conductive material whichalso acts as a diffusion barrier to protect metallization layer 14 fromoxidation, external moisture penetration and upward diffusion of themetallic atoms therein. The liner material 24 may be formed bydeposition of refractory metals or alloys such as (but not limited to)TaN, Ta, TiN, Ti, W, WN, TaSiN, TiSiN, a combination thereof, or anymaterial known to those skilled in the art to be a good liner material.

[0015] In FIG. 4, the liner material 24 formed atop passivation layer 12and mesa 20 is removed. Particularly, the removal of a portion of theliner material 24 atop mesa 20 is done so as to prevent a short circuit(between wiring segments 16) from being created at the bottom of thefuse structure, as opposed to on the top of the completed fusestructure. The remaining liner material 24 following the removal processthus covers the vertical and bottom surfaces of vias 18.

[0016] In order to remove the liner material 24 both atop thepassivation layer 12, as well as the portion atop mesa 20, chemicalmechanical polishing (CMP) with a soft pad is applied thereto. With manyCMP operations, a hard pad is used so as to avoid an undesired dishingeffect in which more material is removed from the central area of apolish than from the sides. In this case, however, dishing is a desiredeffect since the portion of liner material 24 atop mesa 20 sits lowerthan the remaining liner material 24 atop passivation layer 12. Thus, asoft pad is preferred with the CMP process to remove non-coplanar levelsof liner material. As an alternative to a chemical mechanical polish,liner material 24 may also be removed by plasma etching. To remove theportion atop mesa 20, a masked reactive ion etch (RIE) may be used,whereas a blanket RIE may be used to etch back the remainder of linermaterial 24 atop passivation layer 12. Etching is not a preferredremoval process for this step, however, due to the associated cost ofthe photolithography step used to form the mask.

[0017] Next, the inner area 22 (shown in FIGS. 2-4) of the fusestructure is filled with an organic material 26, and planarized to thetop of passivation layer 12, as illustrated in FIG. 5. The organicmaterial 26 will form the encapsulated material of the final fusestructure, and is preferably a spin-on material such as a polyimide, apolyamide, a polyarlyene ether, a polyaromatic hydrocarbon (PAH), aconductive polyaniline, or any other suitable organic material known toone skilled in the art. Examples of such suitable organics include, butare not limited to, SiLK® (manufactured by Dow Chemical Company), Flare(manufactured by Allied Signal Corp.), PAE2, Velox (both manufactured bySchumacher Co.), Ormecon® (developed by Zipperling Kessler & Co., andsold by Honeywell Corporation), diamond-like carbon (DLC), and paralyenecompounds. Furthermore, the organic material 26 may be a gap fillingmaterial (which fills all the way into vias 18 as shown in FIG. 5) or anon-gap filling material, so long as sufficient material is formed ininner area 22 and atop mesa 20. However, a gap filling material ispreferred.

[0018] Referring now to FIG. 6, the organic material 26 is then recessedfrom the top of passivation layer 12 by an O₂ plasma RIE process.Thereby, a recess 28 is created at the top of the fuse structure toallow for the formation of a conductive layer atop the organic material26, as will be described. If oxidation becomes a concern during theorganic recess process, other etch gas chemistries may be used. Otherpossible etch gasses include, but are not limited to, N₂, H₂, NH₃, N₂H₂,CO, CO₂, CH₃F, CH₂F₂, CHF₃, CF₄, or any combination thereof. As analternative to etching, the organic material 26 may also be recessed bychemical mechanical polishing.

[0019] As shown in FIG. 7, a conductive path is created between wiringsegments 16 after the deposition of a conductive layer 30 uponpassivation layer 12, down into recess 28, and across organic material26. The material for conductive layer 30 may be selected from the samematerials as the liner material 24, or from different materialsaltogether. Finally, in FIG. 8, a fuse structure 32 is fully definedafter the removal of the conductive layer from the top of passivationlayer 12. Preferably, the removal is implemented by another CMP step.This time, however, a stiff or hard pad is used in conjunction with thepolishing because dishing is unwanted. Alternatively, an etch processcould be used to remove conductive layer 30 from the top of passivationlayer 12. A negative photo resist (not shown) would preferably coverrecess 28 (as well as the portion of conductive layer located therein).Then, the remaining uncovered conductive layer 30 across the passivationlayer 12 is etched away.

[0020] Thus formed, fuse structure 32 provides an energy-dissipativedevice having an organic material encapsulated beneath a conductivelayer. When the conductive layer 30 of fuse structure 32 is subjected toa beam of energy, such as from a laser, the organic material 26encapsulated underneath the conductive layer 30 is rapidly heated andvolitalized. As a result, the thin conductive layer 30 is explosivelyopened, thereby opening the fuse structure. Because of the presence ofthe organic material 26, the laser energy requirements for blowing thefuse structure 32 are reduced.

[0021] In an alternative embodiment of fuse structure 32, the formationof conductive layer 30 could be eliminated altogether if a suitableelectrically conductive polymer, such as Ormecon® is chosen as theorganic material 26. Referring once again to FIG. 5, the fuse structure32 could be completely defined at that stage of the process if theorganic material 26 were to have sufficiently low resistivity andgap-filling properties so as to complete a circuit between wiringsegments 16. For such an embodiment, the fuse structure 32 would befused open by application of a laser beam directly to the organicmaterial 26, such that the ensuing volatility of the organic material 26creates an open circuit over the top of mesa region 20.

[0022] It will also be appreciated that although the fuse structure 32is described above as preferably being formed within a passivation layer12 of a semiconductor device, the same could also be formed within lowerlevels of the device. For instance, the vias 18 could also be formedwithin an intermediate level of insulation for contact with a lowerwiring layer. In such a configuration, however, no organic materialwould be included at or above the intermediate level. Since any organiclayers not included within a fuse structure would understandably bevolatilized by a laser beam, any semiconductor layers at or above alayer containing such a fuse structure should be organic-free.Furthermore, any insulating layers above a fuse structure 32 formed atlower levels would preferably be thinned or removed altogether by asuitable etch, so as to provide an escape path for the exploded organicmaterial.

[0023] While the invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A laser-programmable fuse structure for anintegrated circuit device, comprising: a conductive layer, saidconductive layer completing a conductive path between wiring segmentsincluded in a wiring layer; and an organic material encapsulatedunderneath said conductive layer; wherein the fuse structure is blownopen by application of a beam of laser energy thereto.
 2. The fusestructure of claim 1, further comprising: a liner material in electricalcontact with said wiring segments and said conductive layer, said linermaterial further encapsulating said organic material between said wiringlayer and said conductive layer.
 3. The fuse structure of claim 1,wherein said organic material is selected from a group that includes apolyimide, a polyamide, a polyarlyene ether, a polyaromatic hydrocarbon(PAH), and a conductive polyaniline.
 4. The fuse structure of claim 1,wherein said liner material is selected from a group that includes TaN,Ta, TiN, Ti, W, WN, TaSiN, TiSiN, or alloys therefrom.
 5. The fusestructure of claim 1, wherein said conductive layer is selected from agroup that includes TaN, Ta, TiN, Ti, W, WN, TaSiN, TiSiN, or alloystherefrom.
 6. The fuse structure of claim 2, further comprising: a pairof vias formed within an insulating layer and extending down to saidwiring segments; and a mesa region of said insulating layer formedbetween said pair of vias; wherein said liner material is formed uponsides of said mesa region and said wiring segments.
 7. The fusestructure of claim 6, wherein said pair of vias is filled with saidorganic material.
 8. The fuse structure of claim 7, wherein said organicmaterial further occupies an inner area of the fuse structure, saidinner area between the top of said mesa region and said conductivelayer.
 9. The fuse structure of claim 8, wherein said conductive layercovers said inner area and said organic material, thereby completingsaid conductive path.
 10. A method for forming a laser-programmable fusestructure for an integrated circuit device, the method comprising:forming a conductive layer to complete a conductive path between wiringsegments included in a wiring layer; and encapsulating an organicmaterial underneath said conductive layer; wherein the fuse structure isblown open by application of a beam of laser energy thereto.
 11. Themethod of claim 10, further comprising: forming a liner material inelectrical contact with said wiring segments and said conductive layer,said liner material further encapsulating said organic material betweensaid wiring layer and said conductive layer.
 12. The method of claim 10,wherein said organic material is selected from a group that includes apolyimide, a polyamide, a polyarlyene ether, a polyaromatic hydrocarbon(PAH), and a conductive polyaniline.
 13. The method of claim 10, whereinsaid liner material is selected from a group that includes TaN, Ta, TiN,Ti, W, WN, TaSiN, TiSiN, or alloys therefrom.
 14. The method of claim10, wherein said conductive layer is selected from a group that includesTaN, Ta, TiN, Ti, W, WN, TaSiN, TiSiN, or alloys therefrom.
 15. Themethod of claim 11, further comprising: forming a pair of vias within aninsulating layer, said vias extending down to said wiring segments; anda mesa region of said insulating layer thereby being formed between saidpair of vias; wherein said liner material is formed upon sides of saidmesa region and said wiring segments.
 16. The method of claim 15,further comprising filling said pair of vias with said organic material.17. The method of claim 16, wherein said organic material furtheroccupies an inner area of the fuse structure, said inner area betweenthe top of said mesa region and said conductive layer.
 18. Alaser-programmable fuse structure for an integrated circuit device,comprising: an electrically conductive organic material, saidelectrically conductive organic material completing a conductive pathbetween wiring segments included in a wiring layer; and saidelectrically conductive organic material further filling a pair of viasformed within an insulating layer, said pair of vias extending down tosaid wiring segments; wherein the fuse structure is blown open byapplication of a beam of laser energy to said electrically conductiveorganic material.